Thin tape for dielectric materials

Abstract

An improved, flexible, strong, thin precursor green tape for dielectric ceramics is described. The tape is prepared from a cellulosic resin of specific characteristics. The tape is especially useful in the preparation of multilayer capacitors and related electronic devices.

What is claimed is: 
     
       1. A green ceramic precursor tape which comprises a free-standing, flexible layer having a thickness not greater than about 25 microns and prepared from a slip composition having: (a) a dielectric component in an amount sufficient to provide the resulting thin film with the desired dielectric properties;   (b) a binder comprising at least one alkylcellulose ether or hydroxyalkylcellulose ether in an amount sufficient to bind the dielectric material into the thin film upon the removal of the solvent; and   (c) a solvent in an amount sufficient to solubilize the dielectric component and the binder and to provide the slip composition with the viscosity required to form the thin film.   
     
     
       2. A tape of claim 1 wherein the dielectric component is barium titanate. 
     
     
       3. A tape of claim 1 wherein the alkylcellulose ether is ethylcellulose. 
     
     
       4. A tape of claim 3 wherein the ethylcellulose has an ethoxyl content of from 44 to 53 weight percent and the viscosity is greater than about 40 centipoise. 
     
     
       5. A tape of claim 4 wherein the ethylcellulose has an ethoxyl content of from 44 to about 50 weight percent and the viscosity is greater than about 40 centipoise. 
     
     
       6. A tape of claim 5 wherein the ethoxyl content is from 48 to about 49.5 weight percent and the viscosity is from 40 to about 60 centipoise, the viscosity being that of a 5 weight percent solution measured at 25° C. in an Ubbelohde viscometer with a solvent which is 80 weight percent toluene and 20 weight percent ethanol. 
     
     
       7. A tape of claim 6 wherein the ethylcellulose is ETHOCEL® 45 brand ethylcellulose. 
     
     
       8. A tape of claim 5 wherein the ethoxyl content is from about 48 to about 49.5 weight percent and the viscosity is from about 90 to about 110 centipoise, the viscosity being that of a 5 weight percent solution measured at 25° C. in an Ubbelohde viscometer with a solvent which is 80 weight percent toluene and 20 weight percent ethanol. 
     
     
       9. A tape of claim 8 wherein the ethylcellulose is ETHOCEL® 100 brand ethylcellulose. 
     
     
       10. A tape of claim 4 having a thickness of from about 5 to about 10 microns. 
     
     
       11. A tape of claim 1 wherein the slip contains a wetting agent or surfactant. 
     
     
       12. A tape of claim 1 wherein the slip contains a plasticizer. 
     
     
       13. A capacitor prepared using a flexible, free-standing green tape having a thickness not greater than 25 microns, the green tape being prepared from a slip comprising: (a) a dielectric component in an amount sufficient to provide the resulting thin film with the desired dielectric properties;   (b) a binder comprising at least one alkylcellulose ether or hydroxyalkylcellulose ether in an amount sufficient to bind the dielectric material into the thin film upon removal of the solvent; and   (c) a solvent in an amount sufficient to solubilize the dielectric component and the binder and to provide the slip composition with the viscosity required to form the thin film.   
     
     
       14. A capacitor of claim 13 wherein the cellulosic resin is ethylcellulose. 
     
     
       15. A capacitor prepared using a flexible, free-standing green tape having a thickness not greater than 25 microns, the green tape being prepared from a slip comprising: (a) a dielectric component of barium titanate in an amount sufficient to provide the resulting thin film with the desired dielectric properties;   (b) a binder of ethylcellulose in an amount sufficient to bind the dielectric material into the thin film upon removal of the solvent; the ethylcellulose having an ethoxyl content of from about 48 to about 49.5 weight percent and a viscosity from about 40 to about 60 centipoise, the viscosity being that of a 5 weight percent solution measured at 25° C. in an Ubbelohde viscometer with a solvent which is 80 percent toluene and 20 weight percent ethanol; and   (c) a solvent in an amount sufficient to solubilize the dielectric component and the binder and to provide the slip composition with the viscosity required to form the thin film.   
     
     
       16. A capacitor prepared using a flexible, free-standing green tape having a thickness not greater than 25 microns, the green tape being prepared from a slip comprising: (a) a dielectric component comprising barium titanate in an amount sufficient to provide the resulting thin film with the desired dielectric properties;   (b) a binder comprising ethylcellulose in an amount sufficient to bind the dielectric material into the thin film upon removal of the solvent; the ethylcellulose having an ethoxyl content of from about 48 to about 49.5 weight percent and a viscosity from about 90 to about 110 centipoise, the viscosity being that of a 5 weight percent solution measured at 25° C. in an Ubbelohde viscometer with a solvent which is 80 weight percent toluene and 20 weight percent ethanol; and   (c) a solvent in an amount sufficient to solubilize the dielectric component and the binder and to provide the slip composition with the viscosity required to form the thin film.   
     
     
       17. A green ceramic precursor tape which comprises a free-standing, flexible unsupported layer having a thickness of from 5 to 18 microns and prepared from a slip composition having: (a) a dielectric component in an amount sufficient to provide the resulting thin film with the desired dielectric properties;   (b) a binder having at least one cellulosic resin in an amount sufficient to bind the dielectric material into the thin film upon removal of the solvent; and   (c) a solvent in an amount sufficient to solubilize the dielectric component and the binder and to provide the slip composition with the viscosity required to form the thin film.   
     
     
       18. A tape of claim 17 having a thickness of from about 5 to about 10 microns. 
     
     
       19. A capacitor prepared using a flexible, free-standing green unsupported tape having a thickness of from 5 to 18 microns, the green tape being prepared from a slip comprising: (a) a dielectric component in an amount sufficient to provide the resulting thin film with the desired dielectric properties;   (b) a binder having at least one cellulosic resin in an amount sufficient to bind the dielectric material into the thin film upon removal of the solvent; and   (c) a solvent in an amount sufficient to solubilize the dielectric component and the binder and to provide the slip composition with the viscosity required to form the thin film.